The Roman Theory of Property Rights

Locke never understood the differences between water and land law. How do we know that? Because if you look at his illustration, he says that if you take water out of a fountain then it's going to be yours by the first possession rule, but of course this is not water sitting in a fountain. It's a very dynamic system, and the question is not is the water yours after you take it out of the fountain, or out of the river. The question is are you allowed to take this amount of water out of the river and why? John Locke says in effect is two things. One he says is you can take water from the river, so long as you leave as much again inside the river. But the moment you think about that you realize there's something deeply wrong with it, because by definition if one person takes something out there's necessarily going to be something less left for the next people on the list. And so if you have to leave as much again and there's a good, in the individual case it means in the end that you cannot allow anybody to take anything out. And then the second kind of limitation that you have is that if you could take it out only to the point that you can make gainful use of it. And that of course turns out not to be a particularly good limitation because what the rule doesn't do is it doesn't take into account the losses to other people even for in stream uses on the one hand, or on the out stream uses. So what they ancients did is they didn't treat this as a question of individual choice. They treated it as a systematic problem, and they said what we are going to do is to allow people to take out water, roughly speaking pro rata to the shore that they have. And then what we do is we create a hierarchy of uses, and the hierarchy of uses is roughly you can first use it to feed your family and to give water to your family. And then to take care of your animals. And to take care of your crops, and for other uses on the land. And it's pro rata. Now how you enforce this is very tricky, and it's done by custom. But essentially, the basic intuition is if everybody's in the same boat, how much is the carrying to passage in the river and then we divide it pro rata.